1. Field of Technology
The present invention relates to a mechanism for locking and unlocking an operable cover in a body representing, for example, a machine such as a printer wherein the cover opens and closes a roll paper compartment and to a printer including a locking/unlocking mechanism for a cover. More specifically, the present invention relates to a locking/unlocking mechanism enabling an operable cover to be easily opened and closed with the cover unaffected by vibration and impact when in the closed position.
2. Description of Related Art
Printers having a compartment for holding roll paper or other continuous form paper inside the printer housing, and printing to the roll paper while pulling it from this compartment, are common. Such printers typically have the print head enclosed within the case of the printer, and a platen roller (paper feed roller) assembled in an operable cover with the platen roller disposed opposite the print head. The operable cover opens and closes an opening in the case for providing access to a roll paper compartment in which roll paper is loaded or removed. Opening the cover opens both the roll paper compartment and the paper path. More specifically, because the platen roller retracts with the cover and opens the paper path when the cover is opened to load or replace the roll paper, roll paper can be easily threaded through the paper path by simply inserting the roll paper in the roll paper compartment and manually pulling the end of the paper out from the compartment, and then closing the cover.
Printers with a cover of this type may also have a lock mechanism to keep the cover locked in the closed position so that the cover does not open unintentionally. This lock mechanism typically has a locking lever assembled to either the cover or the case (body), and a catch disposed on the other side so as to engage the locking lever. In one such arrangement as is described, in Japanese Unexamined Patent Appl. Pub. H09-240083 (see FIG. 6 and FIG. 7), the locking lever can rock longitudinally (front-back) to the printer, and when the cover is closed the locking lever is urged by a spring or other urging means to engage a catch either from the front or back to lock the closed cover.
When a cover locking mechanism and a separate opening mechanism for pushing the cover in the open direction are thus separately provided, an operation for releasing the locked state of the locking mechanism and a separate operation for pushing the cover open by means of the opening mechanism must be sequentially performed to open the cover. This is inconvenient because the cover cannot be opened with a single operation. Opening the cover can be made easier in this case by linking the locking mechanism and opening mechanism so that releasing the locking mechanism triggers the opening mechanism to push the cover open. However, when these operations are linked and the lock is unintentionally released by vibration or impact, the cover is easily and undesirably opened.
The present invention provides a cover locking/unlocking mechanism which permits the cover to be opened and closed with a single operation, and when the cover is in the closed position it is not sensitive to external factors such as vibration and impact.